Moving with the times

The dyes injected into the skin by tattoo artists when creating their artwork move with time – a recently published mathematical model could predict how your body art will look in the future.

Heavy metals used in coloured tattoos can shift with time

Tattoo inks are a suspension of particles which are insoluble in water. Heavy metals – lead, mercury, cadmium, nickel, zinc and iron – are used for colours which are applied as the dermis of the skin is punctured in the desired pattern.

This damage causes an initial immune response where white blood cells clear the debris – some of the ink particles are removed via the lymphatic system, but the remainder are engulfed in fibroblast cells and sealed below the surface. Over time, these dyes move, permanently altering the look if the design.

Dr Ian Eames – a reader in fluid mechanics at University College London – has published a mathematical model in Mathematics Today which estimates the movement of these particles and how specific tattoo designs will look.

“A great deal of work has already been done on the short term fate of ink particles in the skin, tracking them over a period of a few months – but much less is known about how these particles move over longer periods of time,” said Eames.

The paper provides a mathematical framework to help predict how ink particles move over 20 year periods, said Eames. The work paves the way toward assessing whether there are any long term health implications of tattoos as well as giving people an idea of how their chosen design might look several years down the line.

“Skin type, age, size, exposure to sunlight and the type of ink which is used all influence how a tattoo disperses with time,” said Eames. “Broadly speaking, the small details in a tattoo are lost first, the thicker lines being less affected. Although finely detailed tattoos might look good when they are first done, they tend to lose their definition after 15 years – depending on how fine the lines are.”